Pearls are also a June birthstone. We often picture a pearl as simply being a round cream or white coloured gem, a little smaller than a pea, but in fact there are a lot of different shaped and coloured pearls. 

Before we had cultured pearls, the types of pearls used in antique jewellery were seed pearls, half pearls, mabe or blister pearls, and larger natural round or irregular shaped pearls.

Victorian seed pearl earrings

Seed pearls, small round and nearly round pearls generally less than 2mm in diameter, have been used in jewellery for a long time but became popular in the 18th and 19th centuries. They were used to provide a border for a jewel or miniature, for tassels, to encrust a piece in pretty patterns or to imitate a cluster of grapes. They were extensively used for sentimental and mourning jewellery.

Victorian pearl ring

Many of the small pearls you see in antique pieces are half pearls, that is, small pearls that either had been cut away from the shell of the mussel and so had a flat side or were the better halves of defective pearls. They generally ranged in size from .5 mm to .75mm, but could be as big as 4mm in some cases. The centre of the half pearl industry was Idar and in Oberstein in the Duchy of Oldenburg, Germany. Pearls were purchased from India. In the Idar region alone, over 100 workers were employed. Half pearls were used in particular in lockets, watches and as borders for brooches and rings.

Antique insect brooch set with gemstones and a mabe pearl (in Navette on Ruby Lane)

Blister pearls are often referred to as half pearls but they are larger, and grow against the shell wall and not in the tissue. Some blister pearls were produced by the black-winged pearl oyster, the Pteria penguin, which lives in the Red Sea, Indian Ocean and the western Pacific. This oyster is called ‘mabe-gai’ in Japanese and the pearls became called ‘mabé pearls’. This name is now used as a generic term for all blister pearls (M Campbell Pedersen, pp146-7). They were used innovatively in brooches and necklaces. The jewelled insect brooch above is a good example.

While smaller pearls were generally accessible to the middle classes, large natural pearls were the domain of royalty and the very wealthy. It was this market that was most affected when cultured pearls began to be commercially produced in the 20th century.

Next week, I will talk more about the shape and colour of pearls.

A good reference book on pearls, among other things, is:

Maggie Campbell Pedersen, Gems and Ornamental Materials of Organic Origin, 2010